Thin film rust prevention



United States Patent Scotch Plains, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application May 17, 1956 Serial No. 585,394

8 Claims. (Cl. 106-14) This invention relates to a coating composition having rust preventive properties. More specifically, the invention relates to asphalt cutback rust preventive com positions which have been improved in rust preventive and water repellancy properties by inclusion therein of a minor proportion of a zirconium salt of an organic acid.

Solvent-cutback, hard film rust preventives are well known in the art. These are cold-applied compounds used for (l) the protection of metals exposed to a variety of outdoor weather conditions and (2) any general purpose preservation where a dry-to-touch film is desired. These materials generally contain an. asphalt diluted with a petroleum solvent. The compounds are fluid in nature and may be applied to the metal surfaces to be protected by dipping, brushing or spraying. Upon evaporation of the solvent, a thin film, usually about 1 to 5 mils thick, remains on the metal parts to serve as protection against weathering, corrosive fumes, and the like.

It has now been found, and forms the subject of this invention, that zirconium salts of aliphatic monocarboxylic acids having 12 to 24 carbon atoms per molecule, are capable of materially improving the rust preventive properties of these asphalt solvent-cutback compositions. These zirconium salts when blended with a major amount of an asphalt solvent-cutback rust preventive, in proportions ranging from about 0.1 to 10.0% by Weight, and preferably from 0.5 to 3.0% by Weight, based on the total composition, materially increase the effectiveness of the rust preventive composition.

The asphalt cutback type rust preventive compositions of this invention therefore contain (1) a volatile solvent, (2) an asphaltic material capable of forming a film and (3) certain zirconium salts. Additional additives may also be incorporated, such as wetting agents, plasticizers or other corrosion inhibitors.

The cutback asphalt is prepared by blending a petroleum solvent with an asphalt.

to leave a thin hard film. Such a mixture of asphalt and solvent is often called an asphalt cutback.

The rate of drying and the hardness of the asphalt film remaining are controlled by the proper selection of the base asphalt and the volatility of the solvent 'vehicle. For example, if a naphtha solvent is used, the resulting product is of the rapid-drying type, while if The asphalt may be any' of the types of reduced and reduced and oxidized asice a kerosene fraction is used as the solvent vehicle, medium or slow-drying products result.

The solvent can be any normally liquid organic solvent such as hydrocarbon fractions having a boiling range of about 200 to 600 F., e.g. 200 to 400 F. Examples of suitable solvents are petroleum naphthas; aromatic petroleum solvents, such as toluene, xylene, pseudo cumene; kerosenes; and others, and combinations thereof. It is preferred to use aromatic hydrocarbon solvents, since they will form asphalt cutbacks which have less tendency to gel or increase in viscosity upon storage. Chlorinated hydrocarbon solvents may also be used such as chlorobenzene, trichloroethylene, ethylene dichloride, carbon tetrachloride, and others.

The zirconium salts used in the practice of the invention have the general formula:

(RCOOhZr wherein, R is a radical of an aliphatic monocarboxylic acid containing from 11 to 23 carbon atoms, preferably 15 to 19 carbon atoms per molecule. The high molecular weight aliphatic monocarboxylic acids or fatty acids used in preparing the zirconium salt may be either saturated or unsaturated. In general, the salts are prepared from monocarboxylic acids having from about 12 to 24 carbon atoms per molecule and preferably containing about 16 to 20 carbon atoms per molecule. Suitable aliphatic monocarboxylic or fatty acids include saturated fatty acids such as tridecoic, myristic acid, stearic acid, arachidic acid, behenic acid, and the like; unsaturated acids such as oleic acid, erucic acid, linoleic acid, linolenic acid and others. Hydroxy fatty acids such as 12-hydroxy stearic acid and ricinoleic acid may also be used. Naturally occurring fatty acids such as fish oil acids, tallow acid, coconut oil acids, castor oil acids, etc.

may also be utilized either directly or after hydrogenation. Mixtures of these high molecular weight fatty acids, e.g. hydrogenated fish oil acids with oleic acid, in any proportion, are also operable.

Compositions of this invention will contain by weight about (a) 90.0 to 99.9% of cutback asphalt comprising about 30 to of asphalt, e.g. 40 to 60%, and about 30 to 70% of a volatile solvent, e.g. 40 to 60%, and (b) 0.1 to 10.0% by weight of zirconium salt. A preferred composition will contain about 97 to 99.5% by weight of cutback asphalt and 0.5 to 3% by weight of the zirconium salt. Other additives may also be added. The invention is illustrated by the following examples:

EXAMPLE I 0.5% by weight of zirconium stearat-e was added to an asphaltic cutback (Base A), consisting of 50% by weight, of oxidized asphalt having a softening point of 183 F. (ASTM, ball and ring), a penetration of 27 at 77 F. (100 gm./5 seconds), prepared from a Laguinillas crude, and 50% by weight of a petroleum solvent containing 95.5 wt. percent aromatics and having a boiling range of 300-370 F.

EXAMPLE II 2.0% by weight of zirconium stearate was added to the same base stock used in Example I.

These samples were subjected to salt spray exposure tests, which measure the ability of a protectivecoating to prevent the corrosion of steel specimens exposed to a constant mist of brine. 3

These tests were carried out as follows: Two

I 2" x 4" steel panels polished with a 280 grit polish, were immersed in the samples for one minute, withdrawn at the rate of 4" per minute, and then allowed to dry at 77 F. for 24 hours. Thepanels were then placed in a salt spray cabinet, tested and evaluated in accordance with -against corrosion.

the procedure described in Military Specification MIL- C-1 6l73A, which is a well recognized standard test procedure. In this test, the specimens are exposed to a continuous mist 01 spray. of .brine .sodium chloride in water) at 95 F. It lisan extremely severe test for rustpreventive coatings. After .8 days exposure in the salt spray cabinet, the panels were removed, rinsed in methanol, immersed in mineral spirits to remove the asphalt base film, and carefully examined for signs of corrosion.

.Results ofsaltspray exposure tests on the composition of Examples .1 and .II are shown .in Table .1 below:

Talile I .EEFEQT or ZIROONIUM STEARATE ON'IIHE RUSTJBE- VENTI-VE PROPERTIES or ASPHALT OUTBAOKS As seen from the .above table, the inclusion of zirconium stearate with the asphalt cutback materially improved the rust-preventive properties of the composition.

To compare the effectiveness of zirconium with other heavy metal organic salts, three other blends were prepared, one containing 2% by weight of zirconium stearate, one containing 2% by weight of chromium stearate and the third containing 2% by weight of lead stearate. The cutback asphalt (Base B) in these blends consisted of 54.7% of oxidized asphalt having a softening point of 166 F., 36.4% of a petroleum solvent naphtha having 19% aromatics and 8.9% .of pure toluene. All three of these blends were tested for '(l) homogeneity, (2) film appearance and (3) rust preVentiVe ,properties by the salt spray test previously described.

Results of these tests are set forth in Table II below:

Table II 5 properties of this type of rust-preventive, such as drying time, low temperature adhesion to metal surfaces and storage stability.

What is claimed is:

1. .A coating composition adapted to prevent rusting 10 consisting essentially of a major proportion of a cutback asphalt and from about 0.1 to 10.0 wt. percent of a zirconium salt of an aliphatic monocarboxylic acid having about 12 to 24 carbon atoms per molecule.

2. A hard film rust-preventive composition comprising 15 about (a) 90 to 99.9 wt. percent of a cutback asphalt comprising about 30 to 70% by weight of an asphalt having a softening point of from l to 250 F., 30 to 70 weight percent of a volatile solvent; and (b) from about 0.1 to 10% by weight of a zirconium salt of an aliphatic monocarboxylic acid having from about 12 to 24 carbon atoms per molecule.

3. A hard film rust-preventive composition according to claim 2, wherein said zirconium salt is present in amounts of about 0.5 to 3% by weight, based on the .total composition.

4. A hard film rust preventive composition according to claim 2 wherein said monocarboxylic acid contains about 16 to 20 carbon atoms per molecule.

5 A hard film rust-preventive composition which comprises about (a) 97.0 to 99.5% by weight, of a cutback asphalt comprising about 40 to by weight of an asphalt, selected from the group of reduced and reduced and oxidized asphalts, having a softening point of about 160 to 200 F., and about 40 to 60% by weight, of a volatile petroleum hydrocarbon solvent having a boiling range of about 200 to 600 F., and 0.5 to 3.0 weight percent of a zirconium salt of an aliphatic monocarboxylic acid, containing from about 12 to 24 carbon atoms per molecule.

'6. A rust preventive composition according to claim 5 wherein said aliphatic monocarboxylic acid contains from '16 to 20 carbon atoms per molecule.

EFFECT OF METAL STEARA'IES ON THE HOMOGENEITY, FILM-FORMING AND SALT SPRAY .RESISTANCE PROPERTIES .OF .ASPHALT CUTBACKS 'Noturcof Blend Appearance ol Film on Amount of Corrosion on Material Composition @77 F. Polished Steel After 4 Hr. Pollshcd Steel Panels Drying at 77" F. at end of 8 days Base B Llghtmedlum scattered rus n 2wt. percent Zirconium Stearate in Base B.-- Smooth, uniform Continuous, smooth, glossy." No rusti iig. 2wt. percent Chromium Stearateln Basel.-. Appreciable se tling.-- Lumpy, Irregular Very heavy rusting (40- 60925) (pl total surface I rus c 2wt. percent Lead Stearatein Base B --...d0 Many specks, irregular fl1m Light rusting, scattered pin-point rust; dots.

In considering the results of Table II above, it will be'noted that the zirconium stearate blend was smooth and uniform, while the chromium and lead stearates settled out of the composition. This settling is particularly undesirable since it interferes with the commonlyused spray method for applying these rush-preventive compositions to metal surfaces. In addition, the lead and chromium salts cause undesirable gelling or thick ening of the asphalt base.

While the zirconium stearate ,gave a smooth film, the iihns formed by the chromium and lead stearates were "irregular. A continuous, more regular protective coating is more desirable from the standpoint of protection This point .is further illustrated .by the salt spray data. In the 'salt spray test only the zirconium stearate effectively improved the rnst-preventive properties of the asphaltic'film. "The addition of the monocarboxylicacidhaving about 12 to 24 carbon atoms per molecule.

References Cited in the file of this patent 7 UNITED STATES :PATENTS 2,132,997 Plechner Oct. 11, 1938 2,573,878 .Schiermeier etal. Nov. 6, 1951 2,587,777 ,Smith Mar. 4, 1952 

1. A COATING COMPOSITION ADAPTED TO PREVENT RUSTING CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF A CUTBACK ASPHALT AND FROM ABOUT 0.1 TO 10.0 WT. PERCENT OF A ZIRCONIUM SALT OF AN ALIPHATIC MONOCARBOXYLIC ACID HAVING ABOUT 12 TO 24 CARBON ATOMS PER MOLECULE. 